Scroll compressors are widely used for refrigeration and air conditioning systems. They are generally constructed of two scroll members, each having an end plate and a spiral wrap. The scroll members are arranged in an opposing manner with the spiral wraps interfitted, and the scroll members are mounted so that one scroll member moves orbitally with respect to the other scroll member. During this orbiting movement, the spiral wraps define moving fluid pockets which decrease in size as they progress radially inwardly from an outer position at relatively low suction pressure to a central position at relatively high discharge pressure.
The compressed fluid generally exits from a central discharge chamber through a port formed through the end plate of one of the scroll members. This port is usually simply a hole having straight walls formed through the end plate. Because the end plate is relatively thin, as compared to the height of spiral wraps and the size of the central discharge pressure chamber, it has been discovered that the discharge port often acts as a choke plate or throttle to restrict discharge flow. This restriction reduces the efficiency of the scroll compressor.
In addition, the compression ratio of a scroll compressor in operation may fluctuate for a variety of operational reasons, even though the scrolls have a theoretically constant built-in volume ratio. This fluctuation results in over-compression losses or reverse flow and re-compression losses. Also, reverse flow can cause undesirable reverse rotation when the machine is shut down. One method to reduce reverse flow and re-compression losses is the use of a dynamic, one-way valve in the discharge port. Such valves, however, are often noisy, unreliable, and reduce compressor efficiency due to valve losses in normal operation. They also add additional cost for valve and auxiliary hardware, as well as assembly.
The present invention has as its object the obviation of the problems associated with the current art by providing a uniquely configured discharge passage which provides a highly efficient diffuser effect. The diffuser is formed either having a converging portion and a diverging portion, or a diverging portion only, and may be constructed with or without a tail pipe. The diffuser provides efficient flow through enhanced pressure recovery from the central discharge pressure chamber while resisting reverse flow.
The various advantages and features will become apparent from the following descriptions and claims in conjunction with the accompanying drawings: